Gain control circuits



Jan. 24, 1939. 1 G, wlLSCN 2,144,865

GAIN CONTROL CIRCUITS Filed May 28, 1957 a FIG! 4 I l 9 1 /2 /0 i /a C: l C: C"

A TTENUA T'ION NETWORK l l l i my? 42 GEAR/N6 GAL VANOMET E R CON 7' R01.

MECHANISM NETWORK INVENTOR By 6 WILSON v ATTORNEY UNITED STATES PATENT OFFICE GAIN CONTROL CIRCUITS Ira G. Wilson, Brooklyn, N. Y., assigncr to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application May 28, 1937, Serial No. 145,207

9 Claims. (Cl. l78i4) This invention relates to gain control circuits line at each of the attended and unattended gain for a transmission line and particularly to gain control stations. The transmission line may be control circuits which are controlled by pilot a p Of W s in a Cable a the transmission lines. line may be of the carrier type, if so'desired. A

One object of the invention is to provide a service alternating-current motor is prov1ded at 5 transmission system having attended and 1111- each station for governing the operaticliln of the attended gain control stations on a transmission as oc ed amplifier repeater; E913 Service line that shall efiect synchronous operation of m r pr b y Comprises a rotor having a the gain at all stations. three-phase winding and a stator having a sin- Another object of the invention is to provide ale-phase Windin The rotor windings of all 10 ain control circuits for a transmission line havthe m r a connected in parallel circuit relaing an attended gain control station, an unattion and the stator windings of all the motors are tended gain control station and a pilot line assoconnected in parallel circuit relation. 1Apparatus ciated with the line sections controlled by said at an attended sta ion not only contro s the operstations that shall synchronously control the ation of the service motor at the attended station 15 gain at all stations from the attended gain conbut also controls the operation of the service motrol station according to the resistance variations tors at a u ber of u attended Stations. The of the pilot line with temperature changes. service motor at each station controls the asso- A further object of the invention is to provide ciated amp y governing a Condenser 01 a ea transmission line having an attended gain consistance element in the ,8 circuit for the amplifier. 20 trol station, an unattended gain control station One pilot line extends along the line sections and a pilot line associated with the line sections controlled not only by the amplifier at the atcontrolled by said stations with gain control amtended station but also along the line sections plifiers at each of said stations operated by a sercontrolled by the amplifiers at the unattended vice alternating-current motor at each station stations. The pilot line forms a part of a bridge 25 End contrtol circuilts for opgrating thre service mocircuit at the attended stfation. This pilot line ors sync ironous y accor ing to e resistance may e a separa e pair 0 Wires in the cable or changes in the pilot line by temperature changes. may be a direct-current path on the pair of Along signal transmission line is provided with wires forming the transmission line itself, as

reapeatter olr amplifiielr1 statioigs Whl Cl'tl; aretlloczited shown in the application of I. G. Wilson, Serial a 1n erva s a ong e me 0 main am e me N 145,208, filed May 28, 1937.

attenuation constant irrespective of temperature The bridge circuit t t tt t t operchahgessome P the Stations are attended and ates galvanometer control mechanism in accord- Other of h Stahohs ar e uhahtehdedheretofore ance with the resistance changes in the pilot line h station whfether an attended Stahoh an with temperature changes. The galvanometer 35 g g g statlont g p cgmplete as h control mechanism not only controls a resistance a 3 igi sg i e h he z fi a in the bridge to rebalance the bridge but also f 9 me See Ion con m e y operates the rotor of a distributor dynamo-electhe station and the apparatus controlled by the the machine. The distributor dynamo-electric measuring means for operating the amplifier to m Chine which is 0 er ted b th alv nometer 40 compensate for the change in attenuation on t i 1 e g t the line Section A System of the type under Com con mi mechanism, is simi ar in cons me 1011 o the servlce motors located at the unattended and sideration may be the fiat gain regulating system 4 L disclosed in the patent to R A. Brooks attended stations. The three-phase rotor wind- 2,075 975 April 6, 1937 ing of the distributor machine is connected in According to the invention, complete control parallel with the rotor Wihdihgs of h Service apparatus is only provided at an attended motors and the single-phase stator wmding of t and the unattended Stations are operated the distributor machine is not only connected in from attended stations to fi t a Saving in appa parallel to the stator windings of the service moratus at the unattended stations. The invention tors but also sihglejphase Source P P is described means of ire control When the SeI'VlCe machine and the dlstrlbutol circuits of the type disclosed in the above-menmachine are connected as above set forth, y tioned patent to 1". A. Brooks, 2,075,975. movement of the distributor machine rotor will A suitable amplifier which is preferably of the be followed synchronously by the rotors of the thermionic type is provided in a transmission service motors. A motor circuit of this type is 55 disclosed in the patent to C. J. A. Michalke, No. 684,579, dated October 15, 1901.

In gain control circuits as constructed above set forth, a single pilot line will have resistance variations according to all sections of the transmission line and will control the bridge circuit to operate the galvanometer control mechanism according to the attenuation changes in the transmission line. The galvanometer control mechanism not only rebalances the bridge but operates the distributor machine to effect operation of the service motors at the attended and unattended stations. The service motors operate the Various amplifiers at the attended and unattended stations to compensate for any change in attenuation on the transmission line which may be caused by temperature changes.

In the accompanying drawing, Fig. 1 is a diagrammatic view of fiat gain regulating circuits and twist gain regulating circuits for attended and unattended gain control stations.

Fig. 2 is a diagrammatic view of fiat gain regulating means of the type shown in Fig. 1 with the gain of the unattended stations controlled from the attended station.

Fig. 3 is a diagrammatic View of a modified station in the gain control circuits shown in Fig. 2 of the drawing.

Referring to Fig. 1 of the drawing, a transmission line comprising conductors I and 2 is shown provided with two unattended gain control stations 3 and 4 and one attended gain control station 5. Suitable gain control amplifiers 6, 1 and 8 are respectively provided at the stations 3, 4 and 5. The amplifiers 6, I and 8 are for fiat gain control purposes and are shown controlled by separate pilot lines in separate bridge circuits. Pilot lines 9, l and II are respectively provided at the stations 3, 4 and 5, for controlling bridge circuits l2, l3 and I l. The bridge circuits operate apparatus, not shown in Fig. 1, for controlling the amplifiers 6, l and 8.

According to the present invention, the pilot lines 9 and I0 and the bridge circuits l2 and I3 are dispensed with and all control for the unattended stations 3 and 4 is effected from the attended station 5. A twist gain regulator is also shown in Fig. 1 of the drawing. The twist gain regulator is governed by a pilot line l connected to a bridge circuit I6. The pilot line l5 extends along all sections of the transmission line which are controlled by the stations 3, 4 and 5. The bridge circuit I5 controls an'attenuation equalizer [1 in the manner disclosed in the patent to F. A. Brooks, No. 2,075,975. The bridge circuit I6 and the apparatus controlled thereby also makes a correction in the pilot line H for the attended station as indicated by the adjustable resistance I8.

Referring to Fig. 2 of the drawing, a fiat gain regulating system of the type shown in Fig. 1 of the drawing is illustrated with the control of the gain at the unattended stations effected at the attended station. Like parts in the circuit shown in Fig. 2 of the drawing are indicated by similar reference characters. The attended station 5 is provided with a bridge circuit 25 under control of a pilot line 21. The pilot line 21 extends along the sections of the transmission line controlled by the unattended stations 3 and 4 and the attended station 5. Although only two unattended stations are shown in the drawing, it is to be understood that any desired number of unattended stations may be associated with one attended station- The bridge circuit 20 comprises resistance elements 22, 23, 24, 25 and an adjustable resistance element 23. The adjustable resistance element 26 is controlled by a switch arm 21. A battery 28 is connected across two opposite vertices of the bridge, and galvanometer control mechanism 29 is connected across the other two vertices of the bridge. The galvanometer control mechanism 29 may be of the type disclosed in the above-mentioned patent to'F. A. Brooks, No. 2,075,975. The galvanometer control mechanism 29 operates a shaft 35 which, through beveled gears 3| and gearing 32, operates the switch arm 27 to control the resistance 25. The switch arm 27 controls the resistance 25 to rebalance the bridge circuit after each operation of the galvanometer control mechanism 29. The shaft 35 is also connected to the rotor 33 of a distributor dynamo-electric 'machine 35.

The rotor is provided with a three-phase winding and the stator of the machine is provided with a single-phase winding 35 connected to a single-phase source of power 35.

Service alternating-current motors 31, 38 and 39 are respectively provided at the stations 3, i and 5. The service motor 31 is provided with a three-phase rotor winding 49 and a single-phase stator winding 4|. The service motor 38 is pro vided with a three-phase rotor winding 42 and a single-phase stator winding 43. The service motor 39 is provided with a three-phase rotor winding 44 and a single-phase stator winding 45. The three rotor windings 40, 42 and 44 for the service motors 31, 38 and 39 are connected in parallel to the rotor winding for the distributor machine 34 and the stator windings Al, 43 and 45 for the service motors 37, 38 and 39 are connected in parallel to the stator winding 35 and to the source 33. The service motors. '31, 33 and 39 when connected as above set forth will follow any movement effected by the rotor of the distributor machine 34. The distributor machine 34, as before set forth, is operated in accordance with the resistance changes in the pilot line 2!. The pilot line 2! has resistance changes in accordance with temperature changes and according to attenuation changes in the transmission line.

The amplifier 8 at the attended station 5 is controlled by a {i circuit comprising an attenuation network 41, a manually adjustable condenser 48, and an automatically adjustable condenser 49.' The condenser 49 is adjusted under control of the service motor 39 at the attended station 5. The rotor for the service motor 39 at the attended station 5 is connected to gearing 53 by shaft 5! and the gearing 5D in any suitable manner is connected to the adjustable condenser 49 for controlling the [3 circuit of the amplifier 8 according to the operation of the service motor 39. The control of the ,8 circuit for the amplifier 8 is the same as that referred to in the abovementioned patent to F. A. Brooks, No. 2,675,975. In a similar manner, the service motors 3i and 38 at the unattended stations 3 and 4 control the amplifiers 6 and 1. A detail showing of the control at the unattended stations has been deemed unnecessary in view of the showing at the attended station.

Inthe system disclosed in Fig. 2 of the drawing, a change in temperature not only effects a change in the attenuation on the transmission line sections, but also changes the resistance of the pilot line 2|. The pilot line 2| controls the bridge 20 which governs the operation of the galvanometer control mechanism 29. The galvanometer control mechanism 29 rebalances the bridge circuit and effects operation of the distributor machine 34. The distributor machine 34 effects synchronous operation of each of the service motors 37, 38 and 39 at the unattended and attended stations. The service motors 31, 38 and 39 in turn control the gain of the amplifiers B, l' and 8 at the stations 3, 4 and to compensate for any change in attenuation on the transmission line caused by temperature changes.

Referring to Fig. 3 of the drawing, a modified control of an amplifier at one of the stations is illustrated. Although an attended station is illustrated in Fig. 3 of the drawing, it is understood that similar control may be provided at the unattended stations. An amplifier 60 in the transmission line is provided with a ,8 circuit comprising attenuation network 6| and a resistance element 62 which may be composed of silver sulphide, boron or any other suitable resistance material having a high temperature coefficient of resistance. The silver sulphide element 62 is placed in a suitable oven 63 and is heated by a coil 54. The heating coil 64 is connected in circuit with a battery 65 and an adjustable resistance 66. The adjustable resistance 66 is controlled according to the operation of a service motor 6'! which is similar in construction and operation to the service motor 31, 38 and 39 shown in Fig. 2 of the drawing. The service motor 67 is shown comprising a three-phase rotor winding 68 and a single-phase stator winding 69. The rotor is connected through a shaft to gearing H which operates a switch arm 72 for controlling the resistance 66. The resistancev 66 controls the heating of the silver sulphide element 62 and accordingly the gain of the amplifier 6D. A resistance control as above described may be used in the circuit shown in Fig. 2, if so desired.

Modifications in the circuits and in the arrangement and location of parts may be made within the spirit and scope of the invention and such modifications are intended to be covered by the appended claims.

What is claimed is:

1. In combination, a transmission line divided into sections and having an attended gain control station and an unattended control station connected thereto, gain control means at each of said stations for controlling the gain on the transmission line, and means operated according to the temperature changes to which the transmission line sections are subjected to for synchronously operating the control means at said stations to simultaneously change the gain at each station and maintain the line attenuation constant without oscillating action.

2. In combination, a transmission line having an attended gain control station and an unattended gain control station connected thereto, gain control means at each of said stations, an alternating current motor at each of said stations for operating the associated gain control means, a pilot line associated with the transmission line sections controlled by each of said stations and subjected to the same temperature conditions, and means controlled by said pilot line for synchronously operating said motors to simultaneously change the gain at the stations without oscillating action and maintain the line attenuation constant.

3. In combination, a transmission line having an attended gain control station and an unattended gain control station connected thereto, gain control means at each of said stations, an alternating current motor at each of said stations for operating the associated gain control means, a pilot line associated with the transmission line sections controlled by said stations, a bridge circuit at the attended station having said pilot line included in one arm thereof, and means comprising galvanometer mechanism governed by said bridge circuit for synchronously operating said motors to simultaneously control the gain at the stations and maintain the transmission line attenuation constant without oscillatory action.

4. In combination, a transmission line divided into sections and having an attended gain control station and an unattended gain control station connected thereto, a service alternating current motor at each of said stations, means at each station operated by the service motor at the station for controlling the gain at the station, said means at each station having a continuous and uninterrupted action in adjusting the gain when operated by the associated service motor, a pilot line associated with the transmission line sections controlled by said stations, a bridge circuit at the attended station including said pilot line in one arm thereof, and means controlled according to the operation of said bridge circuit for synchronously operating said motors to simultaneously control the gain at the stations and control the attenuation of the transmission line without oscillating action.

5. In combination, a transmission line divided into sections and having an attended gain control station and an unattended gain control station connected thereto, a service alternating current motor at each of said stations, means at each station operated by the service motor at the station for controlling the gain at the station, said means at each station having a continuous and uninterrupted action in adjusting the gain when operated by the associated service motor, a pilot line associated with the transmission line sections controlled by said stations, and means controlled by said pilot line at the attended station for efiecting synchronous operation of the motors at all stations to simultaneously control the gain on the transmission line at each of said stations without oscillatory action.

6. In combination, a transmission line having an attended gain control station and an unattended gain control station connected thereto, an alternating current service motor at each of said stations having a wound rotor and a wound stator, a distributor dynamo electric machine having a rotor winding connected in parallel to the rotor windings of said service motors and a stator winding connected in parallel to the stator windings of said service motors and to a source of alternating current so that any movement of the machine rotor is synchronously followed by the service motor rotors, gain control means at each of said stations operated by the associated service motors, and means for operating the rotor of said machine according to the temperature changes to which the transmission line is subjected to operate said service motors simultaneously, to control the gain at the stations simultaneously and maintain the line attenuation constant.

'7. In combination, a transmission line having an attended gain-control station and an unattended gain control station connected thereto, an alternating current service motor at each of said stations having a wound rotor and a wound stator, a distributor dynamo-electric machine having a rotor winding connected in parallel to the rotor windings of said service motors and a stator winding connected in parallel to the stator windings of said service motors and to a source of alternating current so that any movement of the machine rotor is synchronously followed by the service motor rotors, gain control means at the stations operated by the associated service motors, each of said gain control means having a continuous and uninterrupted action in adjusting the gain when operated by the associated service motor, a pilot line associated with the transmission line sections controlled by said stations, a bridge circuit at said attended station having said pilot line included in one arm thereof, and means governed by said bridge circuit for synchronously operating said motors to control the gain simultaneously at said stations and maintain the transmission line attenuation constant.

8. In combination, a transmission line having an attended gain control station and a number of unattended gain control stations connected thereto, a bridge circuit at the attended station having a pilot line connected thereto, said pilot line being associated with the transmission line sections controlled by the attended and the unattended stations, galvanometer control mechanism at said attended station under control of said bridge for rebalancing said bridge and for operating a master machine having a wound rotor and a wound stator, a service motor at each of said stations having a rotor winding and a stator winding, the rotor windings of said. service motors being connected in parallel to the machine rotor Winding and the stator windings of the service motors being connected in parallel to the stator winding of the machine and to a source of alternating current and means operated by the service motor at each of said stations for simultaneously controlling the gain at each station on the transmission line to maintain the line attenuation constant without hunting action.

9. In combination, a transmission line having a main gain control station and an auxiliary gain control station connected thereto, a gain control amplifier at each of said stations, control means at each of said stations for operating the associated gain control amplifier, and means operated according to the temperature changes to which the transmission line is subjected for synchronously operating said control means at each station from the main station to simultaneously change the gain at each station without oscillatory action and maintain the line attenuation constant.

IRA G. WILSON. 

